A more substantial comment here is that the recent changes in how the archiver works didn't really turn it into a P2P system. Most notably we still rely on a centralized director that: a) spots that more copies are needed, and b) decides what-to-copy-where.

So I propose to call this section "Peer-to-peer topology". And maybe add a paragraph to state that, whereas peers are in general considered to be equal, coordination is currently centralized.

The new specification does not check /mtime/ in the director. It only count the number of effectively present copies to select contents that need or not more copies.
The check of the /mtime/s of /ongoing/ status is now done in the worker only (note: this was previously done twice).

This makes the batches less accurate about contents that really needs archival, but they are generated quicker, and as this check was done anyway in the worker, we can save a db request for each content.